Apparatus and process for forming mats from pourable material



March 3, 1970 w. s. WIRZ 39 973 5 0 "APPARATUS AND PROCESS FOR FORMINGMATS FROM POURABLE MATERIAL Filed April 9, 1968 INVENTOR HALTER G. WIRZUnited States Patent O 3,498,505 APPARATUS AND PROCESS FOR FORMING MATSFROM POURABLE MATERIAL Walter Geza Wirz, Thalwil, Switzerland, assiguorto Fred Fahrni, Zurich, Switzerland Filed Apr. 9, 1968, Ser. No. 719,873Claims priority, application Switzerland, Apr. 20, 1967, 5,659/ 67 Int.Cl. B65g 37/00 US. Cl. 222254 16 Claims ABSTRACT OF THE DISCLOSURE Thepresent invention concerns an apparatus for forming a uniform mat frompourable material on a moving support, using a volumetric fine meteringdevice with a rotating surface provided with sweeps, a guide wall with aguide surface opposite the downwardly moving portion of said surface,and a leveling member disposed in the vicinity of the upper part of theguide surface.

This invention is broadly concerned with a novel apparatus and a newprocess or method for forming a uniform mat from pourable or particlematerial onto a moving support, using a volumetric fine metering devicewith a rotating surface provided with sweeps or vanes, a guide wall witha guide surface opposite the downwardly moving portion of said rotatingsurface, and further a leveling member disposed in the vicinity of theupper part of the guide surface.

The presently known apparatus of the type above mentioned have the gravedisadvantage that sufficiently uniform mats can not be produced. If, forexample, a mat of wood chips, fibers or the like is produced with suchan apparatus and the mat is then pressed in a normally heated press, ithas been found that the pressed board does not have the desireduniformity and accu racy in regards to its thickness and density Theseboards require considerable subsequent treatment as a result of whichthe economy of the method of manufacture suffers.

The invention is based on solving the problem of producing mats orparticle blanks of great uniformity and accuracy from pourable particlesso that the boards obtained by the pressing of such mats are as free aspossible of faults, and thus require no or a minimum of subsequentprocessing, independently of whether narrow or wide mats are formed.

The inventor of the present invention has now found that the abovedisadvantages can be attributed to two causes. First, the extent towhich the cells between the sweeps or vanes of the rotating surface(conveyor member) are filled is not constant since it depends to a greatextent upon the quantity of particles present on the input side of tirefine metering device. In the previously proposed apparatus this quantityof particles is too great and also not sufiiciently constant. This istrue even when the quantity of particles fed to the rotating part of thefine metering dev ce is regulated by special control means, such as by acontents senser which controls by means of electric means the working ofa coarse metering device arranged upstream. Second, the above describedshortcoming resides in the fact that the said cells of the fine meteringdevice are irregularly and jerkily discharged as soon as the materialbeing conveyed ceases to be retained by the said guide surface.

According to this invention there is provided apparatus of the kinddescribed so constructed that the leveling member serves to feed excessmaterial present in the vicinity of the input side of the fine meteringdevice to a conveyor. The conveyor, in turn, serves to convey 3,498,505Patented Mar. 3, 1970 the excess material back to the input side of acoarse metering device which is arranged upstream of the fine meteringdevice. Additionally, in the vicinity of the lower limit of the saidguide surface a movable comb member is provided.

The conveyor member of the fine metering device, provided with a movablesurface and sweeps, is advantageously formed as a conveyor roller whichcooperates, on the one hand, with a rotary leveling roller and, on theother hand, with a rotating comb roller. An arcuate guide wall extendsbetween the leveling and comb rollers. The apparatus thus becomesparticularly compact, economical, sturdy, and maintenance free.

An embodiment, by way of example, of the apparatus and process accordingto the invention is shown diagrammatically in the accompanying drawing.

C arse metering device consists of a conveyor belt 1 arranged to rotatein the direction of the arrow and guided over a roller 2 and a materialretaining metering roller 4 with prongs or fingers 3 which is disposedat a certain level thereabove. The pourable material 5 is poured ontothe conveyor belt from a bin (not shown) in a manner well known. Theheight of the heap of material lying upstream of the metering roller 4can be kept constant Within predetermined limits by means of a suitableconventional control of the bin discharge members.

A bladed delivery roller is designated by 6, and serves to throw theparticles onto a so-called cage roller. This consists of two end plates7 and a plurality of spaced and mutually parallel rods 8. Owing to thefact that the particles pass through the rotating cage roller twice, auniform distribution and loosening or unmatting of the particlesresults.

The particles metered and loosened and unmatting in the mannerdescribed, are now subjected to an accurate metering by means of ametering conveyor roller 9, a leveling roller 13 and a comb roller 17.The actual metermg or conveyor roller 9 rotates about a horizontal axis.The drive is preferably infinitely variable (not shown) so that thequantity fed can be adjusted as required to the desired amount duringthe operation. Sweeping blades 10 or prongs are arranged on the outersurface of the roller 9.

A sheet metal wall 11 together with the part of the roller extendingthereabove forms a kind of storage chamber for the material which isbeing fed. The lower side of the sheet metal member is bent in such amanner that temporarily stored particles of material can not drop outbetween the blades 10 and the wall 11.

An arcuate wall 12 which guides the particles is located at a certainspacing from the blades 10 on the downwardly moving surface portion ofroller 9. This wall is in the shape of a segment, sector or section of ahollow cylinder or hollow tube. Conveyor roller 9 and guide wall 12 thusbound a precisely defined path for the passage of the particles ofmaterial.

The quantity of particles conveyed per unit of time depends only on thespeed of rotation of the roller 9, provided that care is taken tomaintain the degree of filling in the said passage constant. For thispurpose leveling roller 13 is provided. The roller 13 has severalrakelike members 14 which throw excess material onto an oblique plane 15from where the material slides onto a conveyor belt 16 at right anglesto the longitudinal direction of the belt 1. From there it is fed backto the storage bin or the heap of material 5.

It is apparent that the particle flow coming from the coarse meteringdevice must be slightly stronger than the quantity of particles actuallyfed or used. In general, an excess of 10-15% is critical and willsuflice to compensate for unavoidable variations, and to ensure auniform action of the metering device over its whole width. Undercertain circumstances the supply of the particle material will beautomatically regulated in dependence on the excess of material. Forexample a weighing device (not shown) responsive to the materialconveyed on the conveyor belt 16, can be arranged to increase ordecrease the speed of the roller 2 as required.

The angle a which is formed between the lower end of the guide surfaceof wall 12 and a horizontal plane is also of critical importance. Thisangle should be so chosen that with a selected material for the guidewall and with particles having certain properties, the material near thedelivery portion of the guide surface does not suddenly break off andstart to slide and thus destroy the uniformity of the feeding process.It has been found that with a smooth sheet metal guide wall 12 and whenusing wood shavings, an angle a of about 5-10" prevents, on the onehand, a sliding of the material and, on the other hand, is able to keeplow the magnitude of the force required in addition to the gravitationalforce for the further movement of the particles. By gravitational forceis meant that component of the force, which acts parallel to a tangentto the discharge end of the guide wall 12.

The material conveyed as described along the guide surface by means ofthe conveyor roller 9 and under the action of gravity, is now seized bycomb roller 17 which rotates rapidly and counter to the direction offlow of the particles. This roller 17, which is provided with throwingelements 18, projects the material obliquely downwardly. It is possibleto speak of a milling of the particle flow by the blades or prongs ofthe comb roller 17, projecting into the path of movement of thematerial.

A further cage roller 19 with rods 20 separates the now accuratelymetered particle flow, as indicated at 21, as a result of which any rooftile like piling up of the particles is avoided, and the quality of thedistribution is further improved. The mat formed on the uniformly movingconveyor base 23 is designated by 22.

It can be seen from the drawing that the axis of the rollers shownextend in a direction perpendicular to the direction of movement of theconveyor members. All rollers are at least as long as the width of themat 22 to be formed. It is further apparent that the rollers areprovided with end discs or flanges. It is now possible, for example, toprovide the apparatus with two lateral sealing walls, one of whichextends in a plane together with the discs on the end of the shafts onone side of the apparatus and the other in a plane together with all thediscs on the other side. These sealing Walls extending parallel to oneanother can extend as far as the immediate vicinity of the conveyor base23, as a result of which the lateral boundary of the mat 22 will beparticularly sharply defined.

The construction of the apparatus, the arrangement and method of whichhas been described, permits by means of a relatively simple modificationa continuous or periodic control of the quality of the distributionand/or of the weight or the quantity fed. This quality controlmodification consists in connecting to each of the rotating members asimilar more or less long member. All such additional members will be onthe same side of the apparatus, and will be separated from the originalmember only by the end discs. Thus, e.g., the metering conveyor roller 9may be supplemented by a preferably shorter roller which is mounted onthe same shaft. Such an additional unit would normally be separated fromthe mat forming apparatus proper by one of the lateral sealing walls.After carrying out the necessary measurement, the material metered andfed by this additional device is either pressed into test boards orreturned directly to the delivery point.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for forming a uniform mat from pourable material onto amoving support, said apparatus having a coarse metering device and avolumetric fine metering device with a rotating surface provided withsweeps, a guide wall with a guide surface opposite the downwardly movingportion of said rotating surface, and a leveling member disposedadjacent to the upper part of the guide surface characterized in thatsaid leveling member is arranged to convey excess material present inthe vicinity of the input side of the fine metering device to a conveyordevice serving to convey it back to the input of a coarse meteringdevice which is dis-posed upstream of said fine metering device.

2. Apparatus according to claim 1 characterized by a unmattingseparating member provided with apertures, and movably mounted above thesaid fine metering device.

3. Apparatus according to claim 2 characterized in that the lower exitend of the inner guide surface of the guide wall has an inclination suchthat with a selected material and with predetermined properties of theparticles used for the formation of the mat, particles can only slidealong the guide surface if, besides the gravity component, a smalladditional force acts upon the particles in the direction toward thelower edge thereof.

4. Apparatus according to claim 3 characterized by an infinitelyvariable drive for said metering device.

5. Apparatus according to claim 4 characterized in that the coarsemetering device includes a conveyor belt for the material and arotatable and retaining metering member, mounted thereabove.

6. Apparatus according to claim 5 characterized in that the speed of theconveyor belt for the material is controlled in dependence on the excessof material appearing in the fine metering device.

7. Apparatus according to claim 1 characterized in that the lower exitend of the inner guide surface of the guide wall has an inclination suchthat with a selected material and with predetermined properties of theparticles used for the formation of the mat, particles can only slidealong the guide surface if, besides the gravity component, a smalladditional force acts upon the particles in the direction toward thelower edge thereof.

8. Apparatus for forming a uniform mat from pourable material onto amoving support, said apparatus having a coarse metering device and avolumetric fine metering device with a rotating surface provided withsweeps, a guide wall with a guide surface opposite the downwardly movingportion of said rotating surface, and a leveling member disposedadjacent to the upper part of the guide surface characterized in thatsaid leveling member is arranged to convey excess material present inthe vicinity of the input side of the fine metering device to a conveyordevice serving to convey it back to the input of a coarse meteringdevice which is disposed upstream of said fine metering device, and amoving comb member, said moving comb member arranged adjacent to andcooperating with the lower portion of said guide surface.

9. Apparatus according to claim 8 characterized in that the finemetering device is a roller provided with bladed sweeps and in that thesaid guide wall comprises a hollow cylindrical sector spaced from thefree ends of the said sweeps.

10. Apparatus according to claim 9 characterized in that the levelingmember extends over the whole width of the metering roller and comprisesa leveling roller rotatable in the same direction as the said meteringroller whereby said leveling roller removes the excess material andthrows it onto a moving belt to be fed back to the input side of saidcoarse metering device.

11. Apparatus according to claim 10 characterized in that said combmember extends over the whole width of the metering roller and consistsof a comb roller provided with bladed throwing elements, said combroller being rotatable in the same direction as the metering conveyorroller but at a higher peripheral speed than the latter, the saidthrowing elements protruding into the path of movement of materialreaching the end of the guide surface.

12. Apparatus according to claim 9 characterized in that said combmember extends over the whole width of the metering roller and consistsof a comb roller provided with bladed throwing element, said comb rollerbeing rotatable in the same direction as the metering conveyor rollerbut at a higher peripheral speed than the latter, the said throwingelements protruding into the path of movement of material reaching theend of the guide surface.

13. Apparatus according to claim 12 characterized in that between thecomb roller and the moving support, a rotatable and hollow distributingand feed roller is located, the surface of which is provided withapertures for the passage of the material to be distributed.

14. Apparatus according to claim 13 characterized by an unmattingseparating member, said separating member being a hollow roller providedwith apertures and movably mounted above the said fine metering device.

15. A method for forming a mat of pourable material in a uniform layerof constant thickness and constant density comprising the steps offeeding a large quantity References Cited UNITED STATES PATENTS2,668,322 2/ 1954 Weyerhaeuser. 2,737,997 3/ 1956 Himmelheber 222552,822,024 2/ 1958 Himmelheber 222-5 5 RICHARD E. AEGERTER, PrimaryExaminer

